I suspect that the CR got it at least partially right in this case, even though the study is not watertight.
The weather situation as described does seem favourable for radar AP (and possible visual mirage), although I haven't checked the refractivity gradients from the figures and neither (it would appear) did the CR people, relying on the temperature profile alone and general arguments. This might be worth doing, for completeness - there are some RH figures I notice, but not too many.
I'd also note that the meteorological report focuses on the atmosphere to the S and SE of Vandenberg, and specifically notes the likelihood of radar/visual AP in this sector, whereas the initial and major sighting was to the NW. This may not be an issue and these condistions might have been representative of other directions too, but the assumption of isotropy ought not to have been smuggled in without comment
As for the numerous individual and clustered slow targets on the tracking radars, the bird hypothesis strikes me as fairly plausible, although I wouldn't say this is demonstrated in the CR (for example no attempt is made to explain "birds" flying at 80 knots. About 45kt would be the top of the range of airspeed of the fastest common bird, the duck (see CR p.675 Fig.5 for example) and so would imply winds of 35kt. However the wind profile at
shows winds of generally only a few knots peaking at 15kt at 2000ft. Whether ducks tend to flock around Vandenberg anyway is something I couldn't comment on. Gulls would seem more likely given the area and the sort of behaviiour suggested, and they fly much slower so the mismatch gets worse.
In general, though, the fact that similar tracking radar targets were sought and detected on subsequent days argues strongly for usually-unnoticed causes in the local radar environment, and birds seem the best bet in that case. Perhaps some electromechanical tracking anomaly explains excess peak speeds?
I agree with Mike Swords' incidental comments re Thayer's position, and in principle with Mike's point that it would be wrong to dismiss all phenomena in a case because some might be explicable. But it depends critically on which of the phenomena. A truly puzzling unknown might give rise to later secondary sightings that are explainable, and these would not devalue the initial event because the causal shadow of the significant event is cast forwards in time as it were. Similarly a primary sighting that is explainable casts a shadow forwards over later sightings that might seem less explainable, and makes us think that a true UFO appearing in the wake of a proven misinterpretation is less likely than that the later sightings are explainable too. Not that the initial sighting in this case is proven to be explainable, but it very well might be, even tthough I'm suspicious of the CR's miraged ship. The CR says:
"It should be noted that the incident that set off the entire sequence of events was an optical sighting at 8:00 p.m. It appears highly probable that the observer saw the running lights of a ship below the normal horizon, but made visible as a result of mirage. The conditions for such a mirage were present, but it must be pointed out that both the first two witnesses insisted emphatically that the object appeared at an elevation of about 10°. That is too high for a mirage of a ship's lights below the horizon. Hence, either their reports of the elevation angle were incorrect, or some other explanation must be found. However, even experienced observers tend to overestimate elevation angles.
"A further fact is of interest, and that is that, in the Operations Control Center on the date of the second visit to AFB A, one of the operators of a search radar declared that he never saw any ships, that the shipping lanes were too far off the coast for ships to be seen by radar from that location, although the antenna was at an altitude of approximately 1,000 ft. He thereupon switched to his most distant range (80 mi.) and immediately a sprinkling of blips appeared at extreme range. They turned out to be ships, their identity confirmed by their slow speed. Since there is no reason to suppose, from a quick study of weather conditions that night, that anomalous propagation had anything to do with the observation of ships, it must be concluded that they could be seen any time.* The only reasonable explanation of the operator's statement that he never saw ships on the scope is that he had never looked for them. Both the original witnesses indicated that large ships never were seen visually from the coast, and that is undoubtedly correct, because they would be below the horizon. Computations show, however, that, under mirage conditions, the running lights of ships would be visible at the 80 mi. range the radars had indicated."
(*I'm not sure why "there is no reason to suppose that AP had anything to do with" an unusual observation of distant shipping. If conditions were super-refractive as suggested then the radar horizon would be expected to expand and take in surface targets at greater than usual ranges. This doesn't make sense to me at first sight.)
The sighting elevation of 10-15deg is certainly too high for visual mirage of a ship beyond the horizon. The CR position is that since mirage is likely on other grounds then the observer(s) must have grossly everestimated the elevation. It's true that this is a very common tendency. But I'm not convinced that these red and green lights could be the running lights of a ship at 80 miles.
First of all, the refracted image of the ship lights is likely to be if anything less bright than they would normally appear at 80 miles distance (no atmospheric optical process is loss-free I suppose). This isn't something I know enough to callibrate and anyway ships would normally only be seen at such an OTH range by observers in planes, but I shouldn't have thought that ship lights would be strikingly bright at that distance. So why does this light stand out in a clear starry sky for a naked eye observer in the first place, so strikingly that he reports it? Would it be brighter than a bright star? (Maybe Bruce can do a rough calculation from known navigation lamp brighnesses?) It isn't that the first obsertver would have seen detail on the scale of the ship: The total angular width of even a 300ft oil tanker broadside on to the line of sight at 80 miles range would be only about 2.4 arcmin and I very strongly doubt that individual navigation lights would be resolvable - mirage refraction is vertical, of course, lateral "magnification" just does not occur (and the implication that it might occur *simultaneously* with vertical displacement is physically totally unrealistic).
The second observer 3 miles away used 7x binoculars, which would have made it effectively 1/2 the width of the moon and so could have revealed some lateral detail, although it isn'r clear from the report that the elliptical red/green separation occurred laterally or vertically. With the "ship" image in mind we assume laterally, but this is not stated. Red/green separation could occur refractively in a vertical direction. But we come back to the elevation, estimated at 10-15deg by observers #1 and #2 and at an *implied* 10deg or more (10,000ft up at "several miles") by observer#3. This is far too much for a mirage displacement. If there was a source well above the horizon roughly where sighted - albeit still possibly affected by propagation anomalies - it might be preferable to a miraged source below the horizon
I could suggest a possible astronomical source combined with some optical distortion due perhaps to a combination of refraction and a diffusing haze layer at the top of an inversion. The descriptions were of a fuzzy blob of multi-coloured coloured lights. A couple of descriptions *sound* as if the lights looked steady, but original reports would need to be studied and the phrase "fuzzy like a spinning top" is to me strongly suggestive of stellar scintillation.
Note initial reports from observers at home at 8:00pm of the object 10-15deg up at about 280-290 degs. Arcturus, the 3rd brightest star, was about 13.5deg up at 284deg at 8:00. A third observation by Range Control Officer at 8:45pm fixes light at 290deg. At this time Arcturus was at 290deg. (True the RCO's estimates of altitude and range at 8:45pm *imply* an elevation in the order of 10deg at least, whereas Arcturus had descended to about 5deg by this time. But IMO this is a relatively weak point of conflict.) Arcturus, the 3rd brightest NHemisphere star, was much brighter than any other star in that part of the sky and especially if affected by intervening haze/temperature distortions might well have stood out. See below.
Hope this is of some use.